The objectives of this program are to investigate the effects of two vasopressin analogs and an adrenocorticotropic hormone (ACTH) analog on certain cognitive tasks and mood states in elderly patients. Three studies are proposed. In Study 1, the specific objective is to determine if subchronic treatment with 1-Desamino-8-D-Arginine Vasopressin (DDAVP) will improve verbal list learning and other cognitive functions in elderly patients who initially perform poorly on cognitive tasks. Forty patients divided into 2 groups of 20 each will be treated with either adjusted doses of DDAVP of placebo in a 3-week inpatient protocol. Repeated measures of cognitive function, mood, and general behavior will be obtained from both groups before, during, and after treatment. In Study 2, the specific objective is to determine if subchronic treatment with an ACTH 4-9 analog (Org 2766) induces significant mood improvements in elderly patients who have mild to moderate levels of depression. Forty patient who meet screening criteria will be divided into two groups and studied in a 9 week outpatient protocol involving 1 week of baseline assessments, 1 week of placebo treatement, 4 weeks of either active or placebo treatment, and three weeks of followup. In Study 3, the specific objective is to determine if 5 days of inpatient treatment with Desglycinamide-D-Arginine Vasopressin (DGAVP) will improve the cognitive performance of mildly impaired elderly patients. Since DGAVP has not been extensively studied in clinical trials, a related objective is to determine if this neuropeptide exerts side effects that would limit its clinical use. The research design is similar to Study 1. If these initial studies yield promising results, subsequent research will focus on determining the biological and behavioral characteristics of responders and optimal dosage levels and schedules.